The present invention relates to an automatic distribution apparatus for distributing medical liquid, specimens and other samples in liquid state.
In the field of activities where systematic experimental studies about technical reactions of various kinds of materials, for example, are conducted, the automatic distribution apparatus is one of the indispensable facilities. The automatic distribution apparatus automatically performs various operations, for example, taking samples of liquid medicine, etc. out of a plate, or a sample keeping body for keeping the samples and transferring them to other places. The plate is provided with a number of small hollows disposed in a lattice form for storing liquid samples. The elementary action in the distributing operations is sucking up the sample liquids kept in the hollows using distribution tips attached to a distribution head, and discharging them. The distribution tips are replaced with new ones each time the sample liquid is changed to another kind, or at every distributing operation.
There may be two modes in the distributing operation: a case where all of each sample liquid kept in the total hollows of a plate are distributed altogether by a distribution head at once; and a case where only the liquid samples kept in certain specific hollows are distributed. Therefore, the distribution head comes in various configurations: one having a number of distribution tips disposed in a lattice form that corresponds to the arrangement of hollows of a plate; and the other having the distribution tips corresponding to a certain specific row of the hollows of a plate, or in other different tip arrangements. At each distribution operation, a suitable distribution head is selected in accordance with specific objectives of the operation.
It is required that the distribution tips can be replaced within a short period of time. To attain this objective, fitting of the distribution tips to all of the nozzles of a distribution head should be done in one operation. As described earlier, some of the distribution heads must be fitted with distribution tips in a lattice arrangement while other distribution heads require the distribution tips in a line arrangement. In distribution heads of different types that require the distribution tips in different numbers and arrangement, it is essential that the distribution tips be fitted surely and quickly. Because the distribution tips are made of a resin or other such physically weak material to take a long tubular shape, it is also required to pay utmost care not to cause damage to a distribution tip during fitting.
The present invention aims to offer an automatic distribution apparatus in which the distribution tips can be fitted to a distribution head quickly and surely.
The automatic distribution apparatus comprises a distribution head provided with a plurality of nozzles each having a tip for sucking liquid sample at the bottom end, a tip exchange stage on which a tip holder holding a plurality of unused tips upright is placed, and moving means for moving the distribution head up and down relative to the tip holder placed on the tip exchange stage for the purpose of having the bottom ends of the nozzles inserted in the tips held in the tip holder. The tip exchange stage is equipped with a platform for holding a tip holder, thrusting means for thrusting the platform upward, and control means for controlling the thrusting force.
With the above-described structure, where the tip holder is thrust upward by the thrusting means and the thrusting force is controlled to an appropriate level, any predetermined number of distribution tips can be fitted to a distribution head automatically in one operation with high reliability, and a possible breakage of a distribution tip during the fitting action can also be avoided.
It is preferred that the control means can change the thrusting force depending on a number, and a type, of the distribution tips to be fitted at each one operation. Controlling the thrusting force of the thrusting means in accordance with such factors as the number of tips to be fitted to provides the distribution tips with an appropriate cushion power to ensure the fitting at a high certainty.
It is also preferred that an air cylinder is used for the thrusting means, and an air pressure regulator is used for the control means.